Upset Bryson DeChambeau after round one of US Open: "I could've easily shot 2-under"

Bryson DeChambeau says he's 'pretty disappointed' with his performance on day one of the US Open. 

The reigning champion, 31, was among the high-profile golfers to struggle at Oakmont on Thursday and is now in danger of missing the cut.

DeChambeau was among the morning wave and had a decent start considering the bruising challenge the field faced. 

He signed for a 3-over 73 which left him seven shots behind early pacesetter JJ Spaun, who carded a flawless 66. 

"Just didn't get anything out of it," DeChambeau told reporters. 

"I kept it 1-under through seven, through eight, hit a perfect drive on nine and this golf course can come up and get you pretty quick. 

"You've just got to be on your game, and it got me, and I wasn't fully on my game. Pretty disappointed with how I played.

"It's not too far off. [I have just] got to get the putting a little bit more dialled and I'll be right there because 3-over could have easily been 2-under today."

DeChambeau, who was also involved in a bizarre rules incident, came unstuck on the par-5 12th. 

The American's second shot found the back edge of the green from 287 yards but drew a horrible lie. 

DeChambeau said he was trying to hit a 'semi half flop' that 'came out like a jumper and just shot and knuckled right'. It led to a bogey. 

"I'm like, well, horrible decision, but life goes on," he said. 

Despite the start, DeChambeau believes that 3-over could still be the winning score come Sunday evening.

"If it doesn't rain on Saturday then there is probably a decent chance," he said. 

"But I'm looking to shoot under par [tomorrow] and give myself a better chance going into this weekend."

JJ Spaun leads the way

America's JJ Spaun stunned the field with a bogey-free 4-under 66 on Thursday. 

Spaun, who lost to Rory McIlroy in a playoff at The Players in March, was the only player not to drop a shot in the morning wave.

"I kind of came out here with no prior history at Oakmont, not really knowing what to expect even US Open-wise," Spaun said.

"This is only my second one. I don't know if that freed me up in any aspect, but I just tried to kind of take what the course gave me. 

"I hit a lot of good shots and tried to capitalise on any birdie opportunities, which aren't very many out here. 

"But I scrambled really well, too, which is a huge component to playing well at a US Open, let alone shoot a bogey-free round.

"I'm just overly pleased with how I started the tournament."

South Africa's Thriston Lawrence (67), South Korea's Si Woo Kim (68) and Scotland's Robert MacIntyre (70) also started well. 

MacIntyre told reporters that it was the hardest course he has ever played.

"Every shot was on a knife edge," he added. 

The aforementioned McIlroy endured a torrid finish to his opening round.